1. Field of the Invention
This invention relates to the determination of a sulfur level in materials and more particularly, to a method and probe for the rapid determination of a sulfur level or content in molten metals or a partial pressure of sulfur in gases.
2. Description of the Prior Art
It is well known that sulfur in metals such as of pig iron and steels (including alloys) generally give rise to problems such as of deteriorating properties, particularly mechanical strengths, of iron and steel materials except for specific types of materials such as sulfur-containing free-cutting steel. Accordingly, it is necessary to invariably monitor a sulfur level at the time of manufacturing iron and steel so as to keep the sulfur level within a range suitable for individual materials. In order to properly control the sulfur level in these iron and steel materials, it is very important how to determine and analyze the sulfur.
Sulfur has been heretofore analyzed by several methods such as a gravimetric method, a neutralization titration method, an iodometric method and a pararose-aniline absorptiometric method (these methods being prescribed in JIS 1215). All of these methods are disadvantageous in that the analysis time is as long as 10 to several tens minutes. In this connection, there is also known a method in which the sulfur level in metal is measured by an infrared absorption technique (which method being not prescribed in the JIS standards). This method has a merit that the analysis time is an short as 1 to 2 minutes but has a drawback that a great deal of skill is required for sampling and thus a total length of time including the time for sampling and conveying samples is about 5 to 10 minutes and is thus relatively large.
For instance, in the refining of iron and steel, when a long time is required for the analysis of sulfur by the above-mentioned analyzing methods, during the course of desulfurization treatments of molten iron such as in iron ladle, torpedo car, mixer as well as at tapping of blast furnace, or during the desulfurization of molten steel such as in steel ladle as well as at blowing and tapping in converter, there arise problems that proper control of an iron or steel is delayed to give a product of a formulation below standards and that a waiting time for re-blowing and re-treatment becomes long, leading to a much lowering of productivity.
In order to overcome the above problems, the present inventors have made a study on and developed a method of rapidly determining a sulfur level in iron or steel, which has been proposed in Japanese Patent Application No. 31748/1979 and now laid open as a Laid-open No. 124061/1980. Further, we have presented the results of a study, entitled "Electrical Conductivities of CaS-base Solid Sulfides" at the meeting of Japan Institute of Metals on April, 1979. In "Metallurgische Elektrochemie" (1975), at pages 426-427 W. A. Fischer and D. Janke proposed their determination of sulfur in molten copper. Moreover, Ono et al of Kyoto University have published their research work, entitled "Measurement of Partial Pressure of Sulfur by an Electromotive Force method using Sulfide-base Solid Electrolytes" at the meeting of Mining and Metallurgical Institute of Japan, 1980 (publication of preliminary collection of lectures: Apr. 1, 1980).
However, any of these methods are not necessarily satisfactory in practical applications. Then, the present inventors have continued the studies along the line of the idea proposed in Japanese Patent Application No. 31748/1979 and found an improved method and probe effective for the practical applications.